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First published online May 18, 2006
Journal of Experimental Biology 209, 2064-2075 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02227

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The energetic costs of trunk and distal-limb loading during walking and running in guinea fowl Numida meleagris : II. Muscle energy use as indicated by blood flow

David J. Ellerby^* and Richard L. Marsh

Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA

View larger version (27K): [in a new window]   Fig. 1. Organismal oxygen consumption and blood flows in guinea fowl during unloaded, trunk-loaded and distal-limb-loaded running at 1.5 m s-1. (A) Net oxygen consumption, calculated as the mean values during running minus the mean resting value. (B) Cardiac output measured by dilution of the injected microspheres. (C) Summed flow to the brain and abdominal organs. (D) Summed blood flow to all of the leg muscles. Values are means ± s.e.m. (N=6). P values are indicated above each bar.

View larger version (17K): [in a new window]   Fig. 2. Blood flow (mean ± s.e.m., N=6) to the muscles that showed significant changes in flow when guinea fowl carried a load on their backs equal to 23% of body mass. Open bars, control values for unloaded running at 1.5 m s-1; shaded bars, the loaded values. Muscles are grouped into those active during swing and stance as indicated by EMG activity, previously measured during unloaded running. The FT is grouped with the stance muscles under the assumption that all of the increase in flow due to a trunk load is due to stance-phase metabolic activity (see text). Abbreviations are defined in Table 1.

View larger version (17K): [in a new window]   Fig. 3. Blood flow (mean ± s.e.m., N=6) to the muscles that showed significant changes in flow when guinea fowl ran with distal limb loads totaling approximately 5% of body mass. Open bars, control values for unloaded running at 1.5 m s-1; shaded bars, the loaded values. Muscles are grouped into those active during swing and stance as indicated by EMG activity, previously measured during unloaded running. The FT is grouped with the swing-phase muscles under the assumption that all of the increase in flow due to a load on the distal limb is due to swing-phase metabolic activity (see text). Abbreviations are defined in Table 1.

View larger version (17K): [in a new window]   Fig. 4. Fractional delta flow in the leg muscles that have significant changes in blood flow in response to (A) trunk or (B) limb loading. Fractional delta flow is the ratio of the change in flow to an individual muscle divided by the total increase in flow to all of the leg muscles combined. The FT is grouped with the stance muscles for trunk loading and swing-phase muscles for limb loading (see text). Abbreviations for muscle names are given in Table 1.

View larger version (37K): [in a new window]   Fig. 5. Approximate line of action for selected hind limb muscles of the guinea fowl. Blue solid lines and solid red lines indicate the lines of action for stance and swing-phase muscles, respectively, that significantly increase energy use in response to a load on the trunk. broken blue lines indicate biarticular stance-phase muscles that had unchanged (FCLP, postIF and LG) or decreased (IG) energy use in response to trunk loading. The small ambiens muscle, which has a significant increase in flow (Table 1), is not shown. The lines of action are drawn to show the major actions of the muscles at the joints, and do not necessarily indicate precisely the muscle origins and insertions or to quantitatively indicate the moment arms. For muscles sharing a similar line of action, only one line is shown. For the ankle extensors, a common line of action is shown along the tibiotarsus, but separate lines indicate origins and insertions where different.

View larger version (19K): [in a new window]   Fig. 6. Joint angles recorded from a guinea fowl running at 1.5 m s-1 (J. A. Carr and R.L.M., unpublished data).

View larger version (26K): [in a new window]   Fig. 7. Approximate lines of action for selected hindlimb muscles of the guinea fowl. Blue solid lines and solid red lines indicate the lines of action for stance and swing-phase muscles, respectively, that significantly increase energy use in response to a load on the distal limb. The lines of action are drawn to show the major actions of the muscles at the joints, and do not necessarily indicate precisely the muscle origins and insertions or to quantitatively indicate the moment arms.